identify defence barriers to prevent entry of pathogens in humans:

1ST LINE OF DEFENCE

(6)

-SKIN:

Description: the skin continuously grows by new cells being produced from below. Cells fit tightly together to from a protective layer covered by dead cells.

Function: unbroken skin prevents entry of pathogens

lack of water makes it hard for pathogens to live on

constant flaking carries microbes away

-MUCUS MEMBRANE:

Description: in the lining of the digestive, reproductive, respiratory and urinary ducts. Provides a think viscous mucus which traps pathogens

Function: sticky and traps pathogens

more pathogens causes for more mucus to flush them out

can contain the antibody IgA which prevents attachment of microbes

mechanisms such as cilia and sneezing help remove mucus and trapped pathogens

-CILIA:

Description: hair-like projections from cells lining the air passages (trachea and bronchial tubes)

Function: move with wave-like beating motion to push mucus containing pathogens from the lungs to throat, where removed by sneezing or coughing

-CHEMICAL BARRIERS

Description: different chemicals are in different parts of the body (acid in stomach, alkali in small intestine, the enzyme lysosome in the tears)

Function: stomach acid destroys pathogens

alkali destoyrs acid resistant pathogens

lysosome dissolves cell wall of bacteria

-OTHER BODY SECRETIONS

Description: secretions from sweat glands

oily secretions from glands in hair

tears cleanse eyes

urine flushes out urinary tract.

Function: contain chemicals that destroy bacteria and fungi

	Created by shaycrystal4 about 10 years ago

Biology (THE SEARCH FOR BETTER HEALTH) Note on 4. Often we recognise by the symptoms it causes. The immune response is not so obvious, until we recover, created by shaycrystal4 on 19/03/2014.